The mechanical strength of glass-based optical fibers is greatly decreased if scratches are formed on their surfaces. A resin is coated on the surface of a non-armored optical fiber element immediately after spinning to prevent the formation of scratches. A typical conventional coating structure is a double coating structure consisting- of a primary coating layer and a buffer layer formed on the primary coating layer.
A soft resin for primary coating layer having a JIS-A hardness value of 40 or less as specified in the Japanese Industrial Standards (JIS) is used to reduce an optical loss called a microbending loss.
Since glass-based optical fibers have a small core diameter, strict coupling precision is required to couple an optical fiber to a light source or an optical receiver. For this reason, when the end face of the optical fiber is processed, the primary coating layer made of the soft resin must be peeled from the optical fiber element to expose the surface of the non-armored optical fiber element, and high coupling precision must be maintained. Since a large force cannot be applied to the optical fiber element, connection by caulking which has been practiced for a conventional electric cable cannot be used to mount the optical fiber element to a metal member such as a connector. The optical fiber elements must be coupled to each other by an adhesive.
As described above, when an optical fiber element having a conventional coating structure is to be coupled to another component, the coatings must be peeled from the optical fiber elements and the optical fiber elements must be washed. Thereafter, an adhesive must be employed to seal a coupling portion and must be hardened, thus making the end splicing time consuming. In addition, when the buffer layer and the primary layer are peeled from the fiber element, the surface of the non-armored element tends to be damaged. In that case, the mechanical strength at the coupling portion is decreased, and hence the reliability of optical fibers is undesirably decreased.
Since a conventional coating material tends to easily peel from the glass, i.e., has weak adhesion to glass, when an optical fiber is fixed (caulked) the non-armored optical fiber element is undesirably displaced due to a temperature cycle or the like. As a result, the end of the non-armored optical fiber element extends at the terminal portion and collides with the coupled member, thus increasing the optical coupling loss at the terminal portion of the optical fiber.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide an optical fiber element wherein splicing workability at the time of coupling of a terminal portion of an optical fiber to a connector or the like can be improved, and at the same time mechanical reliability at the terminal portion can be improved.
It is another object of the present invention to provide an optical fiber element with a jacket which does not easily peel from an optical fiber element.